"The doctor feels as though it's significant," Black said of Marquis' injury.

Marquis allowed six runs on eight hits with three walks over 5 1/3 innings in a loss to the Cardinals on Friday as he was hit hard and his velocity was down slightly from where it typically is.

It hasn't been determined if or when the 34-year-old Marquis will have surgery to repair the ligament. He is on a one-year deal worth $3 million, which likely means he has thrown his final pitch for the Padres.

Marquis was 9-5 with a 4.05 ERA in 20 starts this season. He was 9-2 with a 3.63 ERA in his first 14 starts and the team was 10-4 in games he started. But he never got that elusive 10th victory, going 0-3 with a 5.13 ERA over his last six starts.

"You look at the win-loss record and the overall ERA, though it has been climbing as of late, and we won a lot of games he started," Black said.

Right-hander Sean O'Sullivan will start in place of Marquis on Wednesday against the Brewers.